In recent years, terrestrial digital broadcasting has spread worldwide. While there are a number of standards relating to terrestrial digital broadcasting, the ATSC (Advanced Television System Committee) standard is employed in the USA, Canada, Mexico, and South Korea. As a modulation method, this ATSC standard employs 8VSB modulation (8-ary Vestigial Sideband Modulation), which is a type of single carrier modulation.
Upon comparison of the ATSC standard with a standard that employs the multi-carrier modulation method of which the Japanese ISDB-T (Integrated Services Digital Broadcasting-Terrestrial) standard is representative, it has been pointed out that the multipath tolerance of the former is inferior. In particular, an extremely low dynamic multipath tolerance is demanded for mobile reception. Due to this, since the start of commercial broadcasting in 1998, no ATSC receiver has existed that, in practice, has acceptable performance for use in a moving vehicle.
However in recent years, due to the progression of digital demodulation technology, the possibility of mobile reception of ATSC signals has become higher. For example, in Patent Document #1, a receiver configuration is disclosed that is based upon, diversity reception and channel, transmission path estimation.
It is per se known that diversity reception mitigates multipath tolerance. In such diversity reception, the reception performance is improved by combining signals received by a plurality of antennas.
Moreover, a receiver configuration based upon channel estimation is replacing the prior art receiver configuration based upon an adaptive equalizer. With current ATSC receivers for fixed reception, a receiver configuration employing an adaptive equalizer has become widely used (refer to Non-Patent Document #1). However, with this prior art adaptive equalization technique, during mobile reception, it is difficult to track along a fast fading channel, and this situation is encountered quite often. In particular, the tracking speed gets lower in the case of a diversity receiver, with which it is also necessary to optimize the diversity combination coefficients, in addition to optimizing the equalization coefficients.
By contrast, with a receiver configuration that is based upon channel estimation, a channel impulse response (hereinafter “CIR”) or a channel frequency response (hereinafter “CFR”) is estimated for each diversity branch (hereinafter “branch”), and, by calculating the optimum diversity combination coefficients and equalization coefficients analytically on the basis of these estimations, it is possible to implement excellent tracking performance even for a fast fading channel.